Disclosed are a data transmission method, an authentication method, and a server. The data transmission method performed by a node among a plurality of nodes connected in a hierarchical structure includes generating a node identity (ID) comprising at least one from among a virtual address for identifying the node and a group key for identifying a group to which the node belongs, generating a signature of the node by using at least one from among the node ID and information about a previous node adjacent to the node, and transmitting a data packet to a server using a node chain formed based on signatures of the nodes.